The invention relates to a brake disc/hub assembly wherein the brake disc is displaceable axially relative to the hub.
Disc brakes may be generally divided into two basic types according to the chosen principle of force application: force generation and adjustment for pad wear on both sides of the brake disc: e.g. a hydraulic fixed caliper disc brake with axially fixed brake disc and force generation on both sides of the brake disc; and force generation and adjustment for pad wear on one side of the brake disc and transmission of the actuation force to the opposite side according to the reaction force principle: e.g. a sliding caliper disc brake, hinged caliper disc brake, and fixed caliper disc brake with displaceable brake disc.
Compressed-air-actuated (pneumatic) disc brakes for heavy commercial vehicles with rim diameters of 15 inches and above utilize the reaction force principle mainly because the arrangement of a compressed air actuating cylinder is possible only on the side of the vehicle wheel open towards the interior of the vehicle, owing to the confined installation conditions around the vehicle wheel (the so-called wheel “envelope”). Such designs are disclosed, for example, in DE 36 10 569 A1, DE 37 16 202 A1, EP 0 531 321 A1 (cf, in particular, the design of the adjusters in the manner of rotary drives) and EP 0 688 404 A1.
Sliding or hinged caliper disc brakes require a component fixed to the axle generally called the “carrier” or “torque” plate which carries or guides the brake pads/linings, absorbs the circumferential forces thereof during brake application, and carries the brake caliper, which is mounted in a coaxially displaceable manner with respect to the vehicle axle. The relative movement executed by the brake caliper with respect to the component fixed to the axle can be divided into a working stroke and a wear stroke. The working stroke is executed with each application of the brake to overcome the release clearance of the brake and to compensate for the elasticities of the brake linings and the caliper arising as force is applied. Depending on the amount of the actuation force and the size of the release clearance, the working stroke is usually less than 4 mm.
By contrast, the wear stroke is the wear adjustment travel executed by the caliper over a large number of brake applications in order to compensate for the pad wear on the reaction side of the brake. The wear stroke is composed of the wear on the outside brake lining together with the wear on the outside disc friction surface, and usually is up to 25 mm.
In the case of a brake construction having a fixed caliper and a displaceable disc, by contrast, the working stroke and wear stroke are produced by displacement of the disc. A fixed caliper brake with electromechanical wear adjustment devices on both sides of a brake disc is known, for example, from EP-B-1 230 491 (having U.S. Pat. No. 6,899,204).
With the construction having a displaceable brake disc, a problem arises in trying to keep the brake disc easily slidable on the guide zone of the hub over its full service life. Because of the confined installation conditions and the harsh environmental stresses, effective sealing is hardly achievable.
Against this background, there is therefore needed a displaceable brake disc, which is suitable for use, in particular, with a pneumatically or electromechanically actuated disc brake having a fixed caliper, and which is well protected against seizure as a result of corrosion and the like.
This, and other needs are provided by a brake disc/hub assembly, including a hub and a brake disc axially displaceable relative to the hub. A sliding sleeve on which the brake disc is arranged non-displaceably relative thereto, is guided in an axially displaceable manner on the hub.
According to the invention, the sliding sleeve, on which the brake disc is arranged non-displaceably relative thereto, is guided in an axially displaceable manner on the hub. The sliding sleeve, together with the hub and/or further elements, may be configured so as to be well protected from corrosion, such that seizure of the brake disc caused by corrosion can be avoided in a constructionally simple manner.
It is especially preferred if, corresponding recesses (in particular semi-cylindrical) recesses are distributed around the internal periphery of the sliding sleeve and around the external periphery of the hub, in which recesses intermediate elements for transmitting torque between the hub and the sliding sleeve are distributed. These elements provide good guidance and secure torque transmission between the sliding sleeve and the hub in a constructionally simple manner.
It is especially preferred if the brake disc has internal toothing and the sliding sleeve has corresponding external toothing and/or receptacles to receive the internal toothing to ensure good torque transmission in this region also. In this manner, low thermal stress on the wheel bearing assembly is also achieved, because the brake disc is not connected directly to the hub, but rather only via the toothing and the sliding sleeve. The axial fixing of the brake disc may be effected, for example, by use of relatively small screws or the like on the sliding sleeve. The solution using receptacles for the internal toothing may, in principle, also be implemented directly on a hub and represents an invention in its own right, which can be used to fix a brake disc even without the sliding sleeve, but which is also advantageously used as a development of the sliding sleeve. In this way, excessive loads that might cause fractures can be largely avoided.
The tooth profile may be configured so that the ingress of cooling air into the brake disc is not prevented if the latter has a plurality of friction rings.
It is especially preferred if at least one wiping and cleaning element and/or a rubbing ring and/or a sealing bellows additionally prevent the penetration of dirt into the sliding sleeve.
Further advantageous embodiments are described and claimed herein.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.